So-called microbubbles having a bubble diameter on the order of 100 μm, because of their large body surface area and long residence time in a liquid as compared to bubbles of ordinary size, are expected to be used in a variety of applications where the physical/chemical characteristics of microbubbles are utilized, including a chemical reaction or transportation of a material at a gas-liquid interface.
Microbubble generating apparatuses generally use a method comprising blowing a gas through a porous body into a liquid.
Among such microbubble generating apparatuses, there is an apparatus which generates microbubbles by supplying a gas from a gas supply device, such as a compressor, through a porous body into a pipe in which water is flowing (see e.g. Japanese Patent Laid-Open Publication No. H8-225094, patent document 1).
Recently developed microbubble generating apparatuses often use a method comprising applying a shear force to the surfaces of bubbles to tear the bubbles apart.
Among such microbubble generating apparatuses, there is a swirling-type microbubble generating apparatus comprising a container body having a conical space, a pressurized liquid introduction inlet tangentially provided on the inner circumferential surface of the container, a gas introduction hole provided in the bottom of the conical space, and a swirling gas-liquid outlet provided at the top of the conical space (see e.g. Japanese Patent Laid-Open Publication No. 2003-205228, patent document 2).